Cardiac arrest, exposure to high voltage power lines and other trauma to the body can result in heart fibrillation which is the rapid and uncoordinated contraction of the cardiac muscle. The use of external defibrillators to restore the heartbeat to its normal pace through the application of an electrical shock is a well recognized and important tool for resuscitating patients. External defibrillation is typically used in emergency settings in which the patient is either unconscious or otherwise unable to communicate.
Automated external defibrillators or AEDs are used by police officers, paramedics and other first-responder emergency medical technicians to resuscitate cardiac arrest patients. It is important that the AEDs carried by these technicians be quickly operational after powering up and that they not provide false alarms that might delay rescue. It is essential that in a high stress situation of cardiac arrest, the technician be able to rely on the operability of the AED. Studies have shown that the chances of successfully resuscitating the patient decreases approximately ten percent per minute following cardiac arrest.
AEDs are portable devices that may find themselves in various locations such as the trunk of a car or storage bin of an emergency vehicle. Because of their portability and the variable locations, AEDs are often subject to extreme temperature variations. The batteries contained within and adapted to power the AED are also subject to these extreme variations. A battery subject to extreme cold will typically take longer to charge the AED than a battery at room temperature and thus, may indicate to the user of an AED a false indication of a low battery. Further, AED electrodes subject to very cold temperatures are likely to freeze and in doing so, provide a false indication that the electrodes are inoperable when in fact, they need only quickly thaw to be operable. There is, therefore, a need for an automated external defibrillator with the ability to sense the temperature of the battery powering the AED and to adjust the operating parameters of the AED according to the sensed temperatures.